Calculate Reverse Polish notation Demo

expr.c

#include <stdio.h>
#include <stdlib.h>


int main (int argc, char * argv[])
{
    int a = 0, b = 0;
    int * stack = malloc(sizeof(int) * 20);
    if (stack == NULL)
        return -1;
    char * cur;
    argc--;
    argv++; // goodbye filename
    while (argc-- > 0) {
        cur = *argv++;
        if (cur[0] == '+') {
            a = *--stack;
            b = *--stack;
            *stack++ = a + b;
        } else if (cur[0] == '*') {
            a = *--stack;
            b = *--stack;
            *stack++ = a * b;
        } else {
            *stack++ = atoi(cur);
        }
    }
    printf("result=%d\n", *--stack);
    free(stack);
    return 0;
}

感觉写了这个之后对指针和数组就理解差不多了。